Spanish Chicken with Chorizo and Potatoes

3 tablespoons regular olive oil
12 chicken thighs (bone in, with skin)
750 grams chorizo sausages, whole if baby ones, or cut into 4-cm chunks if regular-sized
1 kilogram baby potatoes, half the larger ones
2 red onions, peeled and roughly chopped
2 teaspoons dried oregano
grated zest of one orange
salt to taste

Preheat the oven to 220°C/gas mark 7 and place 2 wire racks on the upper and lower thirds. Put the oil in the bottom of 2 shallow roasting tins (I used jelly roll baking trays), about 1 1/2 tablespoons in each. Rub the skin of the chicken in the oil, season with salt accordingly, then turn them skin-side up, 6 pieces in each tin. Divide the chorizo sausages and the new potatoes between the 2 tins.

Sprinkle the onion and the oregano over, then grate the orange zest over the arranged contents of the 2 tins. Cook for 30 minutes, then swap the top tray with the bottom tray in the oven and baste the contents with the orange-colored juices. Continue cooking for about 30 minutes or till chicken is done. 
Serves 6.